Mineral collector compositions and processes

ABSTRACT

Collector compositions of a mixture of a C 6  to C 22  fatty hydroxamic acid and an oil for use in a method the removal of impurities from mineral ores by the froth flotation method. The collectors are prepared by reacting an ester of a C 6  to C 22  fatty acid with a hydroxylamine salt and a base in the presence of an oil and water to produce an alkyl hydroxamate salt; acidifying the alkyl hydroxamate salt, forming an organic layer and an aqueous layer, wherein the organic layer contains a C 6  to C 22  fatty hydroxamic acid substantially free of starting esters and hydrolysis and transesterification products of the ester; and separating the organic layer from the aqueous layer to provide a collector composition of the C 6  to C 22  fatty hydroxamic acid and the oil.

BACKGROUND OF THE INVENTION

[0001] Alkyl or alkaryl hydroxamic acids and their salts are well-knowncollectors for the froth flotation of oxide minerals. Soviet workershave found a variety of applications for such alkyl hydroxamic acids,such as those described by Pradip and Fuerstenau, Mineral Flotation withHydroxamate Collectors, Reagents in the Minerals Industry, Ed. M. J.Jones and R. Oblatt, Inst. Min. Met., London, 1984, pp. 161-168, arecent review that summarizes the flotation application of alkylhydroxamic acids.

[0002] Hydroxamic acids have been used for the flotation of metals orminerals such as pyrochlore, fluorite, huebnerite, wolframite,cassiterite, muscovite, phosphorite, hematite, pyrolusite, rhodonite,chrysocolla, malachite, barite, calcite, and rare-earths. They aregenerally more powerful and more selective then conventional fattyacids, fatty amines, petroleum sulfonates and alkyl sulfates. However,the commercially employed methods of making alkyl or alkaryl hydroxamicacid or its salts are tedious and unsafe from the point of view ofindustrial production.

[0003] A procedure for making potassium alkyl hydroxamate is disclosedin Organic Synthesis, Vol. II, page 67. In the disclosed process,solutions of KOH and NH₂OH.HCl in methanol are combined. After the KClbyproduct is filtered off, the filtrate is combined with a liquidmixture of methyl caprylate and methyl caprate, and, after standing for24 hours, the product crystals are filtered off. Major drawbacks of thismethod include low yields, the use of a large amount of toxic andflammable methanol, and the use of potassium hydroxide, which is moreexpensive than sodium hydroxide. In addition, the industrial scalefiltration of a methanolic reaction mixture is clearly undesirable froma safety standpoint.

[0004] U.S. Pat. No. 3,922,872 to Hartlage claims an improved method ofmaking fatty hydroxamates. Hydroxylamine sulfate and the methyl ester ofa fatty acid are reacted in the presence of dimethylamine in ananhydrous lower alcohol slurry. The free hydroxamic acids formed areneutralized with dimethylamine or an alkali metal base to yield anammonium or alkali metal salt, which precipitates, and is filtered anddried. However, the disclosed procedure also employs flammable loweralcohols, such as methanol, ethanol or isopropanol requiring thefiltration of the final hydroxamic product, which is hazardous.Moreover, because of the heterogeneous nature of the reaction, thereaction rate is very slow, e.g., on the order 15 hours in methanol and5 days in isopropyl alcohol, and the yields are relatively low, i.e., onthe order of about 75 percent.

[0005] Various Russian workers have reported methods for making alkylhydroxamic acids and their salts in aqueous alkaline media. Gorlovski,et al., Vses. Soveshch. po Sintetich. Zhirozamenitelyam,Poverkhnostnoaktivn, Veschestvam i Moyushchim Sredstvam, 3rd, Sb.,Shebekino, 1965, 297-9 Chem. Abst. 66, 4983h, 1967, report theproduction of sodium alkyl hydroxamates by reacting the methyl ester ofa C₇,₉ carboxylic acid with an aqueous solution of hydroxylamine sulfateand NaOH at a molar ratio of 1:1.22:2.2 and a temperature of 55° C. orbelow.

[0006] Shchukina et. al., Khim. Prom., Moscow, 1970, 49(3) 220, report ayield of only 72 to 78 percent of the free C₇,₉ hydroxamic acid byreacting the methyl ester, hydroxylamine sulfate, and sodium hydroxidefor two hours at 20°-25° C. and one hour at 55°-60° C., followed byacidification to pH 4-5 at temperatures below 40° C. Shchukina et al.,in Sin. Primen. Novykh Proverkh. Veshchestv, 1973, 123-31 reported inC.A. 80, 1974, 95199K, also report a simple lab method for theproduction of a reagent designated as IM-50 from C₇₋₉ esters.

[0007] Russian workers, in Russian Patent No. 390,074, Chem. Abst. 79,115162C (1973), and in Zh. Prikl, Khim, (Leningrad) 1972 45(8), 1895-7,Chem. Abstract 78, 29193m 1973, report improved yields with the use of 3to 5 percent of an anionic emulsifier in an alkaline aqueous medium. Theuse of an anionic surfactant such as sodium lauryl sulfate (3-5 percentbased on the weight of the methyl ester), reportedly gave an improvedyield of 61.2 percent for valerihydroaxmic acid and 89 percent forcaprihydroxamic acid. To obtain the claimed yields, however, a 40 molarpercent excess of hydroxylamine hydrochloride or sulfate was required.Moreover, both the sodium salts and the free hydroxamic acids recoveredare solids, which are difficult to handle and process.

[0008] Russian Patent No. 513,970, May 15, 1976, Chem. Abst. 85, 66277g,1976, discloses the formation of a solution of mixed free C₃ to C₁₁hydroxamic acids in hydrocarbons for use as a flotation agent. Thedisclosed hydroxamic acids were formed by treating carboxylate esterswith the sulfate salt of hydroxylamine in an alkali medium, and thentreating the resulting sodium alkyl hydroxamates with a mineral acid inthe presence of 100-250 weight percent of a hydrocarbon containing lessthan 20 percent polar organic components, e.g., higher alcohols oresters. The aqueous layer containing NaCl or Na₂SO₄ was discarded aseffluent. Because of the incomplete reaction of the starting ester, thisprocess is inefficient, producing a product that contains significantquantities of the unreacted starting ester.

[0009] U.S. Pat. No. 4,629,556 discloses the removal of various coloredimpurities from kaolin clays utilizing alkyl, aryl or alkyl arylhydroxamates as collectors. The disclosed hydroxamates are produced byreacting free hydroxylamine with the methyl ester of an organic acidhaving an appropriate length hydrocarbon chain and configuration in anon-aqueous medium, such as methanol, in a manner similar to the methodsdiscussed above.

[0010] U.S. Pat. No. 4,871,466 discloses a method for the production ofalkyl or alkaryl hydroxamic acids and/or salts. In the disclosed method,the methyl or ethyl ester of a fatty acid having 6 to 22 carbon atoms isreacted with a hydroxylamine salt and an alkali metal hydroxide in thepresence of a mixture of water, a C₈ to C₂₂ alcohol, and, preferably, anon-ionic or cationic surfactant. The disclosed reaction results in theformation of a hydroxamate solution, which can be used without furtherprocessing in the froth flotation of non-sulfide minerals, or acidifiedto form a liquid alcohol solution of the acid before use in theflotation process. The disclosed process eliminates the need forhazardous and expensive recovery steps, such as filtration, it isrelatively rapid, taking only three to five hours for completion, andprovides relatively high conversions to hydroxamates. However, the finalproduct of the disclosed method contains some unreacted starting ester.

[0011] Improvements in the industrial production and performance of thealkyl hydroxamate collectors are still required. For example, thehandling of solid products is difficult in large scale of production,and increases the complexity and cost of manufacturing. Although thisproblem may be overcome by carrying out the reaction in the presence ofalcohols, as taught in U.S. Pat. No. 4,871,466, as discussed above, theuse of C₈ to C₂₂ alcohols leads to reduced yields through the competingreaction of transesterification and hydrolysis of the methyl esters,e.g., carboxylic acids and other carbonyl components derived from thestarting ester. In addition, where hydroxamic acid collectors are usedin the flotation process, the shorter chain alcohols, e.g., C₈, canproduce uncontrollable frothing or produce undesirable froth properties,enhancing the recovery of undesirable minerals, and longer chainalcohols, i.e., C₁₀ and above, can reduce frothing substantially, whichis a serious concern in column flotation where a certain amount ofcontrolled froth phase is necessary. Furthermore, in certainapplications, depending on the value mineral being floated, the higheralcohols can adsorb on the value mineral in a reverse configuration,i.e. they can adsorb with the polar group exposed to the water phase,thereby reducing hydrophobicity on the value mineral being imparted bythe alkyl hydroxamic acid, resulting in the reduced recovery of thevalue mineral. The commercial alcohols, which can be expensive, alsohave a very strong, sometimes offensive odor, which varies with chainlength.

[0012] Therefore, there remains a need for alkyl hydroxamic acidcollectors and a process for preparing such collectors that overcome theproblems discussed above. The present invention provides such collectorsand a process for preparing them.

SUMMARY OF THE INVENTION

[0013] The invention is directed to collector compositions for use inthe removal of impurities from mineral ores, and to methods for makingand using such collector compositions. Typically, a collectorcomposition of the invention comprises a mixture of a C₆ to C₂₂ fattyhydroxamic acid and an oil, where the oil is preferably selected fromthe group consisting of hydrocarbon, vegetable, plant, and animal oils,and is most preferably a fatty triglyceride oil. Preferred hydrocarbonoils include, but are not limited to aliphatic hydrocarbons, aromatichydrocarbons, and mixtures thereof, such as benzene, xylene, toluene,mineral oil fractions, kerosene, naphthas, and petroleum fractions.

[0014] Preferably, the hydroxamic acid is present in the compositions ofthe invention in an amount of from about 5 to about 70 percent byweight, more preferably from about 10 to about 50 percent by weight, andthe oil is present in an amount of from about 10 to about 95 percent byweight, more preferably from about 20 to about 70 percent by weight,based upon the weight of the composition. Optionally, the collectorcomposition further comprises up to about 70 percent, preferably, fromabout 10 to about 50 percent by weight, of a frother.

[0015] The collector compositions of the invention may be prepared byreacting an ester of a C₆ to C₂₂ fatty acid with a hydroxylamine salt,preferably, a sulfate or hydrochloride salt of hydroxylamine, and a basein the presence of an oil and water to produce an alkyl hydroxamatesalt. The alkyl hydroxamate salt is then acidified, forming an organiclayer and an aqueous layer, where the organic layer contains a C₆ to C₂₂fatty hydroxamic acid substantially free of hydrolysis andtransesterification products of the ester, and the organic layer isseparated from the aqueous layer to provide a mineral collectorcomposition, comprising a mixture of the C₆ to C₂₂ fatty hydroxamic acidand the oil.

[0016] The benefication performance of the collector compositions of theinvention is significantly improved when compared to prior artcompositions, due to a lack of alcohol and a substantially reducedamount of fatty or starting ester in the collector compositions.Generally, the collector compositions of the invention are substantiallyfree of starting ester, such that the amount by weight of C₆ to C₂₂fatty acid ester or starting ester is less than the amount by weight ofhydroxamic acid. Typically the amount of fatty acid ester or startingester present in the collector compositions of the invention is 50percent less than the amount of hydroxamic acid, preferably, less than20 percent, and, most preferably, less than 10 percent of the amount ofhydroxamic acid.

[0017] Esters useful in the process of forming the collectorcompositions of the invention include, but are not limited to, methyland ethyl esters of caproic acids, enanthic acid, caprylic acid,pelargonic acid, caproic acid, undecanoic acid, lauric acid, tridecanoicacid, myristic acid, pentadeconic acid, palmitic acid, margaric acid,stearic acid, oleic acid, benzoic acid, ethyl benzoic acid, salicylicacid, α-naphthoic acid, β-naphthoic acid, cyclohexyl carboxylic acid,and cyclopentyl carboxylic acid.

[0018] The collector compositions of the invention may be used to removeimpurities from a non-sulfide mineral ores by forming an aqueous slurryof the mineral ore, conditioning the mineral ore slurry with thecollector composition of the invention, which is generally prepared bythe method described above, and separating the impurities and thecollector composition from the mineral ore.

DETAILED DESCRIPTION OF THE INVENTION

[0019] The present invention is directed to useful alkyl hydroxamicacids and the production of such useful alkyl hydroxamic acids by thereaction of the methyl or ethyl ester of a fatty acid having 6 to 22carbon atoms with a hydroxylamine salt and an alkali metal hydroxide inthe presence of water, either a hydrocarbon oil or a fatty oil derivedfrom plants, animals or fish, or mixtures thereof, and, preferably, withan optional non-ionic or cationic surfactant. The resulting alkylhydroxamate salt is subsequently acidified with an acid, and the oil/fatsolution of the hydroxamic acid is separated from the aqueous phase,resulting in the formation of a liquid solution or a paste of thehydroxamic acid. The hydroxamic solution or paste can then be usedwithout further modification in the froth flotation of non-sulfideminerals, such as kaolin clays, or can be further diluted with frothers,such as, e.g., pine oil, aliphatic C₅ to C₈ alcohols, polyglycols,polyglycol ethers, etc., to provide a liquid solution useful in amineral floatation process.

[0020] The hydroxamic acid collector compositions of the invention areproduced in high yields, typically greater than 90 percent by weight,and, typically, contain substantially less unconverted starting esterand undesirable side reaction products resulting fromtransesterification and hydrolysis of the starting ester, such as, forexample, carboxylic acids and other carbonyl products, than prior artcompositions. As a result, the performance of the collector compositionsof the invention is significantly improved when compared to prior artcompositions.

[0021] The process of the invention for producing alkyl hydroxamic acidseliminates the need for hazardous and expensive recovery steps such asfiltration, is relatively rapid, being completed in only 3 to 5 hours,and results in extremely high conversions, i.e., on the order of 90 to100 percent, due to the elimination of competing transesterificationreactions, and, thus, provides higher yields than prior art processes.When the optional surfactant is used in the process of the invention,the amount of the surfactant required is smaller than that required inprior art processes. In contrast to the prior art references discussedabove, the use of an oil as a carrier from the beginning of thehydroxamic acid preparation, affords better dispersion of chemicals,better handling of the reactor in large scale manufacture, more uniformheat distribution, higher yields of hydroxamic acid, and better controlof the reactions and acidification.

[0022] In addition, when utilized in the froth flotation of non-sulfideminerals, the oil solutions of the hydroxamic acids are significantlymore effective than prior art compositions, producing higher valuemineral recovery yields and grades. In general, the oils used tend to befroth neutral, unlike alcohols, having very little effect on froth. Therelative froth neutrality of the oil solutions of the hydroxamic acidsallows the use of separate alcohol frothers to independently control thefroth phase properties as desired.

[0023] With the process of the invention, fatty hydroxamic acids areproduced by reacting a methyl or ethyl ester of a fatty acid having 6 to22 carbon atoms, and, preferably, at least 8 carbon atoms, with ahydroxylamine salt and an alkali metal hydroxide in the presence ofwater, and an oil, selected from the group of hydrocarbon oils, fattyoils, or mixtures thereof. The reaction proceeds according to theequations:

[0024] wherein R is a C₆ to C₂₂ alkyl, a C₆ to C₁₀ aryl, or a C₇ to C₁₄alkaryl group;

[0025] M is an alkali metal;

[0026] R¹ is methyl or ethyl, and

[0027] X is a halide, sulfate, bisulfate, phosphate, nitrate or similaranion residue from a mineral acid.

[0028] Useful acid esters include the methyl and ethyl esters of suchcarboxylic acids as caproic acids (C₆), enanthic acid (C₇), caprylicacid (C₈), pelargonic acid (C₉), caproic acid (C₁₀), undecanoic acid(C₁₁), lauric acid (C₁₂), tridecanoic acid (C₁₂), tridecanoic acid(C₁₃), myristic acid (C₁₄), pentadeconic acid (C₁₅), palmitic acid(C₁₆), margaric acid (C₁₇), stearic acid (C₁₈) and the like, in additionto oleic acid (C₁₈), benzoic acid, ethyl benzoic acid, salicylic acid,α- and β-naphthoic acid, cyclohexyl carboxylic acid, cyclopentylcarboxylic acid etc. Ethyl esters of above carboxylic acids may also beused, but require a higher reaction temperature than the methyl esters.

[0029] Hydroxylamine salts, such as the sulfate or hydrochloride, canalso be used. Suitable alkali metal hydroxides include sodium hydroxide,NaOH, potassium hydroxide, KOH, and the like. Amines such as ammonia,dimethylamine, etc. can be used in place of hydroxides. Suitable acidsare hydrochloric, hydrobromic, sulfuric, nitric, etc.

[0030] As discussed above, the use of a non-ionic or cationic surfactantis preferred. Examples of useful surfactants include non-ionicsurfactants, such as alkyl polyethyleneoxy compounds represented by theformula:

RO(EO)n.H,

[0031] where R is C₈ to C₁₈ alkyl, EO is ethyleneoxy and n is an integerfrom 1 to 10, as well as the reaction products of ethylene oxide andhigher alkylene oxides with active hydrogen compounds, such as phenols,alcohols, carboxylic acids and amines, e.g., alkylphenoxyethyleneoxyethanols. Suitable cationic surfactants include alkyl ammonium orquaternary ammonium salts, e.g., tetraalkyl ammonium chloride orbromide, dodecyl ammonium hydrochloride, dodecyl trimethyl quaternaryammonium chloride and the like, and ethoxylated fatty amines. Othersuitable surfactants are described in McCutcheon's book of detergentsand emulsifiers, the contents of which are incorporated herein byreference. Also included in the aforementioned surfactants areoligomeric and polymerizable surfactants described at pages 319-322 ofBlackley, Emulsion Polymerization Theory and Practice, John Wiley andSons (1975), the contents of which are incorporated herein by reference.Examples of such oligomers include ammonium and alkali metal salts offunctionalized oligomers, sold by Uniroyal Chemical under the trade name“Polywet”, and copolymers of acrylonitrile and acrylic acid havingmolecular weights less than 2,000, which are prepared in the presence ofchain terminating agents such as n-octyl mercaptan. Examples ofpolymerizable surfactants include sodium salts of 9- and10-(acrylamido)stearic acid and the like. The effective amounts of thesurfactant range from about 0.5 to 3 percent by weight, of the alkylester, preferably about 1 to 2 percent by weight, same basis.

[0032] The reaction temperature can range from about 15° to 55° C.,preferably from about 25° to 35°. The amount of water used should besufficient to dissolve the hydroxylamine salt, and can vary from about15-50 percent, generally depending on the concentration of thehydroxylamine salt solution. The amount of oil used in the reaction canalso vary from about 15 to 50 percent, and is preferably sufficient tokeep the reaction mixture liquid throughout the course of the reactionat the selected temperature.

[0033] The oil can be any suitable oil that will provide the result ofthe invention, such as hydrocarbon oils, including, but not limited to,an aliphatic hydrocarbons, aromatic hydrocarbons, and mixtures ofaliphatic and aromatic hydrocarbons. Preferred hydrocarbon oils include,but are not limited to, benzene, xylene, toluene, mineral oil fractions,kerosene, naphthas, petroleum fractions, and the like. Most preferredhydrocarbon oils are low odor hydrocarbon oils, preferably a paraffinoil, containing less than about 1 percent aromatics. The oil can also bea fatty oil, such as a triglyceride oil, which is an ester of glycerolwith fatty acids, substantially free of polar components, such ashydroxyl groups. These triglyceride oils are most often derived fromanimals, plants or fish by rendering, pressing, or solvent extraction.Fatty oils that can be used include, but are not limited to, soybeanoil, corn oil, canola oil, sunflower oil, peanut oil, cod liver oil,shark liver oil, and similar plant, animal and fish oils. The oil usedin the present invention can also be a mixture of a hydrocarbon oil anda fatty oil.

[0034] When the reaction between the methyl ester and hydroxylamine iscomplete, and the alkyl hydroxamate salt has been formed, thehydroxamate salt is acidified by the addition of acid, forming twophases, which should be maintained at a temperature sufficiently high toavoid the solidification of the organic product phase. The aqueous phaseis then removed decantation or by the method disclosed in U.S. Pat No.3,933,872, incorporated herein by reference. The organic phase containsthe alkyl hydroxamic acid collector, and is useful as a flotationcollector, either as formed or after addition of a frother and/or otheradditives. Useful frothers include pine oil, aliphatic C₅ to C₈alcohols, polyglycols, polyglycol ethers, etc. Other types of additivesmay be also incorporated into the diluent system specifically to improveperformance. Examples of useful additives include petroleum sulfonates,sulfosuccinates, ethoxylated or propoxylated alcohol surfactants, etc.,which boost the performance of alkyl hydroxamic acids.

[0035] The present invention is also directed to the novel compositionsproduced by the above-described process. The compositions of theinvention comprise a fatty hydroxamic acid, a hydrocarbon oil or fattyoil, and, optionally, a frother or other additive incorporated into thediluent system to improve performance. Where a surfactant is used in theproduction of the fatty hydroxamic acids of the invention, residualsurfactant may also be present in the composition. The alkyl hydroxamicacid content ranges from about 5 percent to about 70 percent, preferablyfrom about 10 percent to about 50 percent, and the oil content rangesfrom about 10 percent to about 95 percent, preferably from about 20percent to about 70 percent. If frothers are added, they may be used inan amount of up to about 70 percent of the total composition, preferablyin the range of about 10 to about 50 percent. If other additives areincorporated to boost the performance, they may be used in amountsranging up to about 20 percent of the diluent, preferably about 5 about10 percent.

[0036] The above-described compositions are useful in the frothflotation of non-sulfide mineral ores, such as those mentioned above,including copper ores, iron ores, rare and rare earth metal ores, and,more particularly, in the benefication of clays.

[0037] Useful flotation methods are well established, and are known tothose of ordinary skill in the art. The methods generally comprisegrinding of ore to liberate mineral values and provide ore particleshaving a size suitable for flotation. The ground ore pulp is pHadjusted, and conditioned with pre-selected and prescribed reagents,such as collectors, frothers, modifier, and dispersants. With some ores,such as glass sands, clays, tailing, etc., the as-mined feed material isalready finely divided and, therefore, no additional grinding isrequired.

[0038] In the case of the beneficiation of clays, for example,substantially no grinding of the as-mined feed is required, because theaverage particle size is of the order of a few microns. The majorimpurities in kaolin clays are anatase, TiO₂, and complex iron minerals,which impart color to the clay, and decrease its brightness, thus makingthe clay unsuitable for many of its applications where purity andbrightness are absolutely essential. Conventionally, the removal of suchimpurities is accomplished by a variety of methods, an important onebeing flotation using tall oil fatty acid.

[0039] In the froth flotation for beneficating clay, where the clay isslurried in an aqueous medium, conditioned with an effective amount of adispersing agent and collector, and floated, the method of the inventioncomprises employing as the collector the novel compositions above, i.e.,the hydroxamic acid solution, in quantities ranging from about 0.1 toabout 18 pounds per ton of ore, preferably 0.5 to 6 pounds per ton. Thenovel process of the present invention results in the recovery of claysin high yields, having low TiO₂ content and increased brightness.

[0040] As a first step in carrying out such a process, the clay to bepurified is blunged in water, i.e., mixed with water to form asuspension, at an appropriate solids concentration, as described in U.S.Pat. No. 4,629,556, the contents of which are incorporated herein byreference. A relatively high pulp density, in the range of about 35 toabout 70 percent by weight solids, is preferred since the interparticlescrubbing action in such pulp helps liberate colored impurities from thesurfaces of the clay particles.

[0041] Following conventional practice, a suitable dispersant, such assodium silicate, polyacrylate, or polyphosphate, is added duringblunging in an amount, e.g., about 1 to about 20 lb. per ton of drysolids, sufficient to produce a well-dispersed clay slip. An alkali,such as ammonium hydroxide, is also added, as needed, to produce a pHabove about 6, and preferably is the range of about 8 to about 10.5. Inaccordance with the invention, the hydroxamate collector is then addedto the dispersed clay under conditions, i.e., proper agitation speed,optimum pulp density, and adequate temperature, which permit reactionbetween the collector and the colored impurities of the clay in arelatively short time, generally not longer than about 5 to about 15minutes.

[0042] When the clay has been conditioned after the addition ofcollector, it is transferred to a flotation cell, and typically dilutedto a pulp density that is preferably in the range of about 15 to about45 percent by weight solids. The operation of the froth flotationmachine is conducted in conventional fashion. After an appropriateperiod of operation, during which the titaniferous impurities areremoved with the foam, the clay suspension remaining in the flotationcell can be leached for the removal of residual iron oxides, filtered,and dried in any conventional fashion known in the art.

EXAMPLES

[0043] The following non-limiting examples are merely illustrative ofthe preferred embodiments of the present invention, and are not to beconstrued as limiting the invention, the scope of which is defined bythe appended claims. All parts and percentages are by weight unlessotherwise specified.

Comparative Example A

[0044] Following the procedure of Wang, as set forth in U.S. Pat. No4,871,466, for comparative purposes, 107 parts of hydroxylamine sulfatewere dissolved in 264.4 parts of water in a suitable three-neck reactionvessel equipped with a condenser, a mechanically-driven stirrer and athermometer. After the hydroxylamine sulfate was dissolved, 273.8 partsof dodecyl alcohol, 4.8 parts of a 50 percent dioctyl/decyl dimethylammonium chloride surfactant, and 200 parts of methyl caprylate/caprate,the starting ester, were introduced. The reaction mixture was cooled to10-15° C. with stirring in an ice/water bath, and 200 parts of a 50percent sodium hydroxide (NaOH) solution was added slowly through anaddition funnel. During the addition of sodium hydroxide, thetemperature was maintained at 15 to 20° C. After the caustic addition,the temperature was allowed to rise to 25° C., and the reaction wascontinued for 4 to 5 hours at 25 to 30° C. At the completion of thereaction, i.e., when the IR spectrum of the reaction mixture showed notrace of the ester band at 1175 cm⁻¹, 225.4 parts of 30 percent sulfuricacid were added to the reaction mixture, and two phases formed and wereseparated. A titration analysis of the upper organic layer (513.7parts), a solution of the hydroxamic acid in dodecyl alcohol, indicated32 percent hydroxamic acid in contrast to the theoretical yield of 39.2percent, representing an 81.7% yield based on the amount of startingester. An NMR analysis indicated the presence of other components in theorganic layer, including 7.1 percent by weight of the unreacted methylcaprylate/caprate, 8.6 percent by weight C₈ to C₁₀ carboxylic acidsderived from the starting methyl esters, and 7.1 percent by weight ofother carbonyl components derived from the starting ester, where thepercentages are based only on the total weight of hydroxamic acid,unreacted ester, and other reaction products in the alcohol solvent. Thehydroxamic acid amount was 77.2 percent.

Comparative Example B

[0045] Following the procedure described in Russian patent 513,970 forcomparative purposes, 992 parts of an aqueous 12 percent solution ofhydroxylamine sulfate were introduced into a suitable three-neckreaction vessel equipped with a condenser, a mechanically-drivenstirrer, and a thermometer. Following the addition of the hydroxylaminesulfate solution, 168.5 parts of methyl caprylate/caprate were added,followed by the slow addition with stirring of 162.4 parts of a 50percent sodium hydroxide solution through an addition funnel over aperiod of 30 minutes. During the addition of the sodium hydroxide, thetemperature was maintained at 26° to 28° C. After the caustic addition,the reaction was continued for 2 hours, while continuing to maintain thetemperature at 26° to 28° C. After the two hour hold period, 79.46 partsof concentrated sulfuric acid (96.4%) were added slowly, and thetemperature was allowed to increase to 40° C. to keep the resultinghydroxamic acid in liquid form. At this time, 169.5 parts of kerosenewere added, and the acid/kerosene layer was separated from the bottomaqueous layer. The product layer (344.85 parts) was analyzed bytitration, and found to contain 17.4 percent by weight hydroxamate incontrast to the theoretical yield of 50 percent by weight, representinga 35% yield of alkyl hydroxamic acid. The percentage of hydroxamic acidwas 35%, of other carbonyl components was 14% and of starting ester was51%, as determined by NMR. The weight ratio of starting ester to alkylhydroxamic acid, as measured using NMR analysis, was 1.46 to 1.

Comparative Example C

[0046] The process of Comparative Example B was repeated using 496 partsof a 12 percent hydroxylamine sulfate solution, 84.25 parts methylcaprylate/caprate, 81.2 parts of a 50 percent NaOH solution, and 39.73parts sulfuric acid. Again the temperature after the addition ofsulfuric acid was allowed to rise to 40° C., and 211.9 parts of kerosenewere added. The upper organic layer was separated from the aqueous layerand analyzed by titration, indicating a 10.54 percent by weight yield ofhydroxamate in contrast to the theoretical yield of 28.57 percent byweight, representing a 37 percent yield. The NMR analysis showed 37%hydroxamic acid, 13% other carbonyl components and 50% starting ester.The weight ratio of starting ester to alkyl hydroxamic acid, as measuredusing NMR analysis, was 1.36 to 1.

EXAMPLE 1

[0047] In a suitable three-neck reaction vessel, equipped with acondenser, a mechanically-driven stirrer, and a thermometer, 1627 partsof hydroxylamine sulfate were dissolved in 4066 parts of water, and 4145parts of soybean oil, 67 parts of a 50 percent dioctyl/decyl dimethylammonium chloride surfactant, and 3036 parts of methyl caprylate/capratewere introduced. The reaction mixture was cooled to about 10 to about15° C. with stirring in an ice/water bath, and 3028 parts of 50 percentsodium hydroxide was then added slowly through an additional funnelmaintaining the temperature at about 15 to about 20° C. throughout theaddition. After the addition of the sodium hydroxide, the temperaturewas allowed to rise to 25° C., and the reaction was continued for about4 to 5 hours at a temperature of about 25 to about 30° C. The completionof the reaction was determined from the IR spectrum of the reactionmixture, which showed no trace of the ester band at 1175 cm⁻¹. Twophases were formed by the addition of 5120 parts of 18.76 percentsulfuric acid, and separated, while maintaining the temperature abovethe solidification temperature of the hydroxamic acid, e.g., about 30°to 40° C. The upper organic layer, 7719 parts, was found to contain 38.5percent by weight free hydroxamic acid, corresponding to a 97.5 percentyield, when compared to the theoretical yield of 39.5 percent. Onlytraces of starting methyl ester and acids derived by hydrolysis werepresent, as evidenced by the high yield of product. The organicsolution, which was obtained by phase separation, was compatible withtall oil fatty acids, contained capryl/capra hydroxamic acid in soybeanoil, and was liquid at temperatures above about 30° C., and a paste atlower temperature.

EXAMPLE 2

[0048] The procedure described in Example 1 was repeated. However,following the acidification and separation of the phases, 1281 parts ofalcohol frother MIBC were added. The resulting liquid product had ahydroxamic acid of content of 32.7 percent, and remained liquid at atemperature of 20° C. The liquid product was again found to becompatible with tall oil fatty acid.

EXAMPLE 3

[0049] The procedure of Example 1 was repeated, replacing the soybeanoil being with hydrocarbon oil, Escaid 110. Following phase separation,the hydroxamate content of the resulting oil solution was 39 percent,representing a 98.7 percent yield of hydroxamic acid. NMR analysisshowed the presence of less than 3 percent starting ester and carboxylicacid. The product was substantially free of starting ester, having aweight ratio of unconverted starting ester to alkyl hydroxamate of only0.02 to 1. The solidification point of the product was 32° C.

EXAMPLE 4

[0050] The procedure of Example 1 was repeated, replacing the soybeanoil with a corn oil. Following phase separation, the hydroxamate contentof the resulting oil solution was 38.9 percent, representing a 98.5percent yield of hydroxamic acid, and the solidification point was about30° C.

EXAMPLES 5 - 8

[0051] The procedure of Example 1 was again followed, except that themethyl caprylate/caprate was replaced by an equivalent amount of methylstearate, Example 5, ethyl oleate, Example 6, methyl palmitate, Example7, or methyl napththolate, Example 8. Similar conversions of the methylesters to hydroxamic acids were achieved, and solidification point weresimilar to those obtained in Example 1.

EXAMPLES 9 - 15

[0052] Four thousand parts of fresh kaolin dry basis were blunged atabout 60 percent solids for six minutes in a laboratory Morehouse CowlesDissolver, Model: W12, with water and 6 parts of sodium silicate. Aprescribed amount of collector, along with AEROFROTH™ 70 Frother, wasthen added to the well dispersed clay slurry, and the mixture wasconditioned in the same blunger for an additional six minutes.

[0053] After conditioning, the entire pulp was diluted with water to 20percent solids. A sufficient amount of the diluted pulp was taken toprovide 2000 parts of fresh kaolin clay in a 4.5 liter laboratory Denverflotation cell. Flotation was carried out at 20 percent solids bycarefully regulating the air flow for up to 15 minutes while agitatingat 1200 rpm.

[0054] Flotation of this kaolin clay sample, designated Sample A, wassignificantly improved with the novel collectors of the presentinvention, Examples 9 to 14, when compared to the plant standardco-collector system, which is a 1/1 combination of tall oil with acollector made in accordance with U.S. Pat. No. 4,871,466, a commercialalkyl hydroxamate collector product used in Example 15. The results ofthe comparison are provided in Table I. TABLE I Results of DenverFlotation Test Work on Kaolin Sample A EXAMPLE COLLECTOR FROTHER YIELDTiO₂ No. Type Lbs/T Type Lbs/T % %  9 1:1 Ex. 3/Fatty 2 AF-70 0.25 80.10.801 Acid 10 1:1 Ex. 3/Fatty 4 AF-70 0.25 82.4 0.538 Acid 11 Example 32 AF-70 0.25 84.7 0.440 12 Example 3 1 AF-70 0.50 95.6 0.548 13 1:1 Ex.1/Ex. 3 1.5 AF-70 0.50 74.3 0.501 14 Example 1 1.25 AF-70 0.25 87.60.346 15 commercial 1 Tall 1 83.6 0.800 collector Oil

EXAMPLE 16

[0055] The alkyl hydroxamate composition of Example 1 was ted at adosage of 1.25 Lbs./T with 0.25 Lbs./T of AF-70 frother using alaboratory column cell incorporating microcell bubble generator system.The clay yield was 97.8 percent and the TiO₂ content of the flotationproduct was 0.421 percent.

EXAMPLES 17-29

[0056] Flotation tests were carried out on three additional kaolin claysamples designated here as clay samples B, C and D. These crude claysamples had characteristics as summarized in Table II below: TABLE IICharacteristics of Clay Samples B, C and D % Crude Crude GE Passing %Pass Type ID No. Bright TiO₂ Fe % 2.0 nm 0.2 nm Fine C 82.81 2.446 1.37587.7 46.4 Coarse B 84.38 1.730 0.357 63.8 15.2 Coarse D 84.74 1.7830.781 76.5 23.5

[0057] A Premier Mill Agitator blunger was used to blunge 796 parts offresh wet kaolin clay, equivalent to about 651 parts dry solids, withwater and 1.3 parts of sodium silicate at 60 percent solids for 6minutes. A prescribed amount of collector, either a collector of thepresent invention or a prior art collector for comparison purposes, wasthen added to the well dispersed clay slurry, and the mixture wasconditioned in the blunger for an additional 6 minutes. The conditionedpulp was then transferred to a 2.3 liter flotation cell, diluted withwater to about 25 percent solids, agitated at 1000 rpm, and floated witha carefully regulated air flow in the range of about 0.1 to 1.5 1/min ofair for up to about 30 minutes.

[0058] The floated product containing colored impurities, mostlytitaniferous minerals and anatase impurities, and the unfloated cellproduct, containing the clean and bright clay values, were filtered,dried, and assayed for TiO₂ and Fe₂O₃. The results are set forth in theTable III below: TABLE III Na. Na. Example Clay Solids Sil. NaOH PulpTemp Coll. Sil. NaOH Pulp Temp GE Yield TiO₂ Fe₂O₃ No. Collector Sample% Lb/T Lb/T pH ° C. Lb/T Lb/T Lb/T pH ° C. Bright % % % None B 84.4100.0 1.730 0.357 17 Example 2 B 60.0 2.6 3.1 8.2 54.0 2.5 0.0 2.3 8.962.0 88.5 59.8 0.389 0.398 18 85:15 Ex. 3/ B 60.0 1.8 3.1 8.1 52.0 2.50.0 2.3 9.0 64.0 89.6 53.3 0.238 0.379 MIBC 19 Example 3 B 60.0 1.8 3.18.3 52.0 2.5 0.0 2.3 9.1 58.0 89.8 46.7 0.261 0.367 20 Tall Oil B 60.01.8 3.1 8.2 54.0 2.5 0.0 2.3 9.0 56.0 88.7 38.3 0.476 0.387 21commercial B 60.0 1.8 3.1 8.1 52.0 2.5 0.0 2.3 8.9 57.0 90.4 46.7 0.2450.397 None C 82.8 100.0 2.448 1.375 22 Example 1 C 60.0 11.4 2.3 8.250.0 3.6 0.0 1.2 9.0 58.0 86.3 60.5 0.962 1.345 23 Tall Oil C 60.0 10.52.3 8.1 50.0 3.6 1.8 1.2 8.9 58.0 84.4 67.9 1.732 1.349 24 commercial C60.0 8.8 2.3 8.1 45.0 2.0 3.1 1.2 8.8 56.0 85.6 61.1 1.368 1.379 25Example 3 C 60.0 8.8 2.3 8.2 48.0 2.0 3.1 1.2 8.9 58.0 86.8 44.7 1.1681.351 None D 84.74 100.0 1.783 0.781 26 Example 3 D 60.0 1.8 1.5 8.242.0 2.5 5.8 0.5 9.1 45.0 89.2 57.5 0.530 0.738 27 commercial D 60.0 1.81.5 8.0 42.0 2.5 5.8 0.5 9.1 45.0 87.9 70.7 0.809 0.769 28 Example 1 D60.0 1.8 1.5 8.2 42.0 2.5 5.3 0.5 9.2 44.0 88.2 64.2 0.657 0.744 29 TallOil D 60.0 1.8 1.5 8.2 42.0 2.5 5.3 0.4 9.2 42.0 86.2 59.9 1.060 0.783

[0059] The results for crude clay sample B demonstrate the superiorityof the novel collectors of the present invention over both the standardtall oil fatty acid and the commercial collector of Example 15. The bestperformer on this crude, based on both product yield and TiO₂ reduction,was the composition of Example 2, which produced a clay product with ayield of 60 percent at a TiO₂ grade of 0.39 percent, as well as a higherGE brightness.

[0060] With fine crude clay sample C, the collectors of the inventionagain surpassed the flotation performance of both the standard tall oilfatty acid and AP-6493. The best performer with this crude was thecollector of Example 1, which produced the greatest reduction in TiO₂level at a comparable product yield of 61 percent.

[0061] Coarse crude clay D responded to the standard tall oil floatationvery poorly, giving TiO₂ reduction of only 0.8 percent, with a productyield of 60 percent. The newly invented collectors, along with thecommercial collector, produced much improved flotation performance ascompared to the standard fatty acid tall oil system. Both thecompositions of Examples 1 and 3 produced significantly better TiO₂reductions than the commercial collector, at 0.53 percent and 0.66percent, but lower product yields of 58 percent and 64 percent,respectively, as compared to the commercial collector's 0.81 percentTiO₂ and 70 percent yield.

[0062] While it is apparent that the invention disclosed herein is wellcalculated to fulfill the objects stated above, it will be appreciatedthat numerous modifications and embodiments may be devised by thoseskilled in the art. Therefore, it is intended that the appended claimscover all such modifications and embodiments that fall within the truespirit and scope of the present invention.

We claim:
 1. A method for preparing a mineral collector composition, themethod comprising: reacting an ester of a C₆ to C₂₂ fatty acid with ahydroxylamine salt and a base in the presence of an oil and water toproduce an alkyl hydroxamate salt; then acidifying the alkyl hydroxamatesalt, forming an organic layer and an aqueous layer; and separating theorganic layer from the aqueous layer to provide a mineral collectorcomposition, comprising a mixture of the C₆ to C₂₂ fatty hydroxamic acidand the oil.
 2. The method of claim 1, wherein the organic layercontains a C₆ to C₂₂ fatty hydroxamic acid substantially free ofstarting esters and hydrolysis and transesterification products of theester.
 3. The method of claim 1, further comprising selecting the oilfrom the group consisting of hydrocarbon, vegetable, plant, and animaloils.
 4. The method of claim 3, wherein the oil is a fatty triglycerideoil.
 5. The method of claim 1, further comprising forming the hydroxamicsalt in a yield of at least 90 percent by weight.
 6. The method of claim1, further comprising selecting the ester from the group consisting ofmethyl and ethyl esters of caproic acids, enanthic acid, caprylic acid,pelargonic acid, caproic acid, undecanoic acid, lauric acid, tridecanoicacid, tridecanoic acid, myristic acid, pentadeconic acid, palmitic acid,margaric acid, stearic acid, oleic acid, benzoic acid, ethyl benzoicacid, salicylic acid, α-naphthoic acid, β-naphthoic acid, cyclohexylcarboxylic acid, and cyclopentyl carboxylic acid.
 7. The methodaccording to claim 1, wherein the hydroxylamine salt is a sulfate orhydrochloride salt.
 8. The method according to claim 1, furthercomprising maintaining the organic layer at a temperature above that atwhich the hydroxamic acid solidifies.
 9. A method for the removal ofimpurities from a non-sulfide mineral ores, the method comprising:forming an aqueous slurry of the mineral ore, conditioning the mineralore slurry with the mineral collector composition comprising a mixtureof a C₆ to C₂₂ fatty hydroxamic acid, an oil, and an amount of startingC₆ to C₂₂ ester that is less than that of the C₆ to C₂₂ fatty hydroxamicacid, and separating the impurities and the mineral collectorcomposition from the mineral ore slurry.
 10. The method according toclaim 9, wherein the non-sulfide mineral ore is kaolin clay.
 11. Themethod of claim 9 wherein the amount of the starting C₆ to C₂₂ esterpresent in the collector composition is less than 50 percent of theamount of C₆ to C₂₂ fatty hydroxamic acid.
 12. The method of claim 9,wherein the amount of the starting C₆ to C₂₂ ester present in thecollector composition is less than 10 percent of the amount of C₆ to C₂₂fatty hydroxamic acid.
 13. The method of claim 9, wherein the collectorcomposition is substantially free of the starting C₆ to C₂₂ ester. 14.The method of claim 9, wherein the oil is a hydrocarbon oil selectedfrom the group consisting of aliphatic hydrocarbons, aromatichydrocarbons, and mixtures thereof.
 15. The method of claim 14, whereinthe oil selected from the group consisting of benzene, xylene, toluene,mineral oil fractions, kerosene, naphthas, and petroleum fractions. 16.The method of claim 9, wherein the oil is selected from the groupconsisting of vegetable oils, plant oils, animal oils, and mixturesthereof.
 17. The method of claim 16, wherein the oil is a vegetable oilor a fatty triglyceride oil.
 18. The method of claim 9, wherein thehydroxamic acid is present in an amount of from about 5 to about 70percent by weight, and the oil is present in an amount of from about 10to about 95 percent by weight, based upon the weight of the composition.19. The method of claim 18, further comprising a frother in an amount ofup to about 70 percent by weight.
 20. The method of claim 19, whereinthe frother is an alcohol present in an amount of from about 10 to about50 percent.